pre-commit: add spelling check

Check for any changed .rst files in the doc/ directory and run
`make spelling` if any changes are detected.

The files directives per hook have to be more restrictive than the
global hook, so this also slightly changes the files match for
the other hooks.

.pre-commit-config.yaml

@@ -1,11 +1,20 @@
-files: "(console_conf|subiquity|subiquitycore|system_setup)"
+files: "(console_conf|subiquity|subiquitycore|system_setup|doc)"
 repos:
   - repo: https://github.com/psf/black
     rev: 23.7.0
     hooks:
       - id: black
+        files: "(console_conf|subiquity|subiquitycore|system_setup)"
   - repo: https://github.com/pycqa/isort
     rev: 5.12.0
     hooks:
       - id: isort
         name: isort
+        files: "(console_conf|subiquity|subiquitycore|system_setup)"
+  - repo: local
+    hooks:
+      - id: doc-spelling
+        name: doc-spelling
+        language: system
+        entry: bash -c "cd doc/ && ./pre-commit-spell-check"
+        files: "doc/.*rst"

doc/pre-commit-spell-check

@@ -0,0 +1,8 @@
+#!/usr/bin/env bash
+
+# Setup sphinx virtual env if it's not already
+if [ ! -d .sphinx/venv ]; then
+    make install
+fi
+
+make spelling